DE68906915T2 - PACKING WITH Tearable film. - Google Patents

Abstract

A package (1) for extended storage and in-store display of fresh red meat is disclosed. Preferably the package (1) is made by a vacuum skin packaging process wherein the forming web is a composite peelable film (3) having a peelable oxygen barrier layer (4) and an oxygen permeable skin layer (5) which remains to enclose the product (8) when the peelable film (4) is removed after storing. A means and method for readily initiating the peeling process is provided by a combination of a manual pull tab (18) and selected perforations (17) of the forming web.

Description

Field of the invention

This invention relates generally to packages having a peelable film or skin. More particularly, the present invention relates to vacuum skin packages in which a barrier layer or layers can be peeled and separated from a non-barrier layer or layers due to the package configuration providing easy initiation of the peeling process. This invention further relates to a vacuum skin packaging method utilizing this package configuration.

Background of the invention

Skin wrapping can be classified as a forming process for thermoformable polymer films. However, the term "vacuum skin wrapping" or VSP as used hereinafter does not refer to the fact that the thermoformable film is formed around the product by means of vacuum or air pressure differential, which is actually the case, but rather to the fact that the product is packaged under vacuum, whereby the space containing the product is evacuated. For a number of products, there is a need for the film formed around each product to be a barrier to oxygen, air and other gases.

Conventional skin packaging uses a support pad that is porous or perforated so that a vacuum can be drawn directly through the support pad. Vacuum skin packaging processes generally use a vacuum chamber with an open top. A product on an impermeable support pad is placed on a platform within the vacuum chamber. The opening to the upper chamber is covered with a film that is sealed to the chamber to form a vacuum-tight seal. The chamber is evacuated while the film is heated to its forming and softening temperature. heated. The platform is then raised to press the product into the softened film and positive air pressure is used above the film to press it tightly around the product. A similar process is disclosed in FR-A-1 258 357, issued to Alain G. Bresson on March 6, 1961.

In another version of prior art vacuum skin packaging, disclosed in US-A-3,491,504, issued to W.E. Young et al. on January 27, 1970, a heat-softened film is physically moved downward over a stationary product and using differential air pressure, the softened thermoplastic film is molded onto the product.

In US-RE 30,009, reissued May 29, 1979 to Richard R. Perdue et al., a thermally deformable or heat-softenable film is drawn against the concave interior surface of the top of a vacuum chamber by means of varying air pressure, then the film is heated by surface contact, and then after evacuating the chamber, air pressure is used to blow the film downward over the product and against the support pad. The resulting package comprises the product placed on the gas-impermeable support pad. The product is held on the support pad by the thermally deformable film which has been molded around the product in the exact shape of the product so that it appears to be a nearly invisible "skin." The thermally deformable film or forming sheet is also gas-impermeable, as previously stated, and is usually made up of a number of layers, each of which performs a specific function. The layer in contact with the product and the support member is a sealable or heat-sealable layer. An inner layer is typically a barrier layer comprising a vinylidene chloride copolymer or a hydrolyzed ethylene/vinyl acetate copolymer, and the outer surface layer is a protective layer to protect the barrier layer from scratches, pinholes and moisture.

In US-A-3,574,642, issued April 13, 1971 to Carl Frederick Weinke, a package for a meat packaging process has been disclosed. The package includes an inner oxygen permeable element, which may also be gas flushed or evacuated. The package preserves the freshness of the meat until the meat is ready to be marketed to the consumer. For marketing, the outer wrapper is removed and the inner package is presented to the consumer. Because it is oxygen permeable, the inner wrapper allows oxygen to pass into the interior of the package, causing the fresh meat product to take on a bright red color that the consumer associates with freshness. The inner bag of the Weinke package may be made of polyethylene film and the outer bag may be a regenerated cellulose film (such as cellophane) with a Saran (vinylidene chloride copolymer) coating. Another patent showing portions of fresh meat individually packaged in an oxygen-permeable plastic film and inserted into an outer container of impermeable film is American patent US 3,681,092 issued to Oliver R. Titchnell et al. on August 1, 1972.

Another prior art package is described in U.S. Patent No. 3,713,849 issued to Paul E. Grindrod et al. on January 30, 1973. The Grindrod et al. patent describes a fresh meat package having an outer oxygen impermeable layer that is easily and completely peelable from an inner oxygen permeable layer. The package includes means for initiating peel separation along one edge of the package. The outer oxygen barrier keeps meat in a well-preserved condition despite the purple color, which has little appeal to the consumer. Shortly before display for sale to the consumer the outer layer is removed by the retailer and the product develops a healthy, bright red "bloom" due to the high oxygen permeability of the inner remaining film package. The material disclosed by Grindrod et al. is a laminate of PVC/Saran and EVA/Saran. (EVA refers to ethylene/vinyl acetate copolymer and PVC refers to polyvinyl chloride.) The EVA and PVC layers are the inner layers and are sealed together at the periphery of the package. The Saran layers can be easily peeled away from the respective EVA or PVC layer using the provided grip strips.

Another peelable package is shown in US-A-4,055,672, issued October 25, 1977 to Arthur Hirsch et al. In the Hirsch et al. patent, a semi-rigid preformed tub is formed of oxygen impermeable material, a meat product is placed therein, and then the tub is sealed around its upper periphery or flange area with a composite lid having an inner layer of oxygen impermeable material, an adhesive layer, and an outer layer of oxygen impermeable material. When the package is ready for retail sale, the impermeable lid is peeled away so that oxygen can pass through the remaining area of the lid and reach the fresh meat packaged within the impermeable material. Therefore, it is a further object of the present invention to provide a package with a separable or peelable barrier layer that is an improvement over known packages.

In a number of cases, in order to preserve a meat product within an impermeable film, it is desirable to create a modified atmosphere which may include an inert gas such as nitrogen or the like, or an atmosphere comprising a mixture of gases such as oxygen and carbon dioxide, to control bacterial growth within the package. Typical packages are shown in the U.S.-A-RE 27,872, issued January 8, 1974 to JH Estes, US-A-2,623,826, issued December 30, 1952 to Sanford R. Grinstead, US-A-3,360,382, issued December 26, 1987 to HV Miller, US-A-4,522,835, issued June 11, 1985 to Richard E. Woodriff, GB-A-1,199,998, published July 22, 1970, CA-A-890,166, issued January 18, 1972 to Charles M. Davison et al., GB-A-1,378,140, published December 18, 1974 and GB-A-1,186,978, published April 8, 1970. US-A-2,925,346, issued February 16, 1960, describes a method of packaging cured meat products and inhibiting color degradation by removing oxygen and backfilling the container with a gaseous nitrogen oxide. Accordingly, another object of the present invention is to provide a vacuum skin package suitable for and usable with modified atmospheres.

In order to easily open packages when plastic film layers have been sealed together to close the package, various pull tabs and easy-open mechanisms have been devised. One such easy-open delamination seal is disclosed in U.S. Patent No. 4,638,913, issued January 27, 1987 to Milton A. Howe, Jr. In this patent, two graspable folds of film are provided to act as gripping strips, and the folds, when pulled apart, tear one of the outer layers of the sealed film and delaminate the film to its edge. In such a case, the bond strength between the two films sealed together must be greater than the bond strength between the layers of film. Accordingly, it is another object of the invention to provide a package that is easy to light.

The foregoing and other objects are achieved by the present invention, which is described in the following summary of the invention, an embodiment of which is set forth in the attached drawings and which is further described in the detailed description. The advantages of the invention will become clear to those skilled in the art upon reading the description.

Summary of the invention

In one aspect, the present invention according to claim 1 is a package with a peelable film layer which

- a product,

- a carrier web on whose upper surface the product lies, the carrier web having at least one edge,

- a composite film as a forming web enclosing the product, the composite film:

a skin layer sealed to the carrier web around the periphery of the product and a peelable layer co-extruded or laminated to the skin layer on the outside of the package, the adhesive strength between the peelable layer and the skin layer being of such a strength that the two layers can be manually delaminated from each other and the adhesive strength being less than the seal strength between the skin layer and the carrier web,

- a header strip sealed to the upper surface of the backing web adjacent to an edge thereof, the composite film being disposed over the strip but not adhering thereto, and both the header strip and the composite film terminating at the edge of the backing element, whereby the composite film is readily separable from the header strip at that edge and forms a manually graspable pull strip, and

- a series of perforations in the composite film arranged substantially in a line generally parallel to the edge of the forehead, closest to the product, with each perforation extending through the composite film and the row being located immediately adjacent to the forehead,

- wherein the tear strength of the peelable layer along the line of perforations is greater than that of the skin layer, whereby when the pull tab is manually lifted, the peelable layer does not tear along that line but the skin layer tears as it remains sealed to the carrier web while the peelable layer is peeled off.

Further preferred embodiments of this packaging are defined in subclaims 2 to 13.

In another aspect, the invention according to claim 14 is a vacuum skin process in which a product is packaged between a forming web and a carrier web and in this process

- a non-adhesive surface is formed adjacent to an edge of the carrier web,

- a forming web with manually separable layers is formed, which

a peelable barrier film and a gas-permeable film, the tear strength of the skin film being lower than that of the peelable film,

- a vacuum skin package is formed, wherein the forming web is sealed to the carrier web around the periphery of the product, the product is spaced from the non-adhesive surface in the unsealed area of the forming web above the non-adhesive area, thereby forming a strip for manual pulling, and the seal strength of the skin film to the carrier web is greater than the tear strength of the skin film, and

- the forming web is perforated with a plurality of perforations in a line adjacent to the non-adhesive surface whereby, when the pulling strip is manually pulled away from the carrier member, the skin film tears and releases the release film to be peeled from the skin film.

Further preferred embodiments of this method are defined in subclaims 15 to 17.

Description of the drawings

Attached and forming part of the description are drawings of illustrative embodiments of the invention, wherein:

Figure 1 is a partial cross-section of a package embodying the present invention and showing the manually grippable pull tab,

Figure 2 is the same view as Figure 1, but illustrates the beginning of the stripping process,

Figure 3 is a schematic representation of a plan view of a series of packages made according to the present invention as they are moved from a vacuum packaging station to a cutting station, the packages being arranged on a carrier web in rows and columns,

Figure 4 is an enlargement of a portion of Figure 3,

Figure 5 is a schematic representation of the edge of a package immediately before the perforation process,

Figure 6 shows a continuation of the perforation process shown in Figure 5 and the preferred depth of penetration of the perforating knife or element,

Figure 7 shows a column of packages with the rows of perforations adjacent to the pull tab of each edge of the packages and

Figure 8 is a plan view of one of the packages of the column shown in Figure 7 which has been cut into an individual package.

Detailed description

In Figure 1, an embodiment of the present invention is represented by the packaging 1. The packaging 1 comprises a carrier element or carrier web 2 on which the product 8 has been arranged. The product is preferably a piece of fresh red meat such as beef, lamb or veal and in most embodiments is a piece of beef such as a fillet or beefsteak.

The carrier web 2 or support member may be a flat sheet of thermoplastic material, preferably polyvinyl chloride, with a coating of a vinylidene chloride copolymer, commonly known as Saran. Any of the vinylidene chloride copolymers that are good barriers to gas may be used, including vinyl chloride comonomer and methyl acrylate copolymer. The shape of the carrier web 2 is illustrated as flat, but may be formed into a tub.

Stretched over the product 8 and closely conforming to the shape of the product 8 is the composite film 3 which is hermetically sealed to the carrier web 2 around the periphery of the product 8 to enclose the product in a gas-tight manner. A preferred method of forming the composite film or web 3 over and around the product 8 and in a hermetically sealed condition with the carrier web 2 is to use a vacuum skin packaging process, preferably as disclosed in the above-mentioned US-RE 30 009. When the composite film 3 is formed over the product 8 in a vacuum skin packaging process, the composite film 3 is referred to as a forming web.

The composite film or forming web 3 comprises a peelable film 4 and a skin film or sealable film 5. The skin film 5 may be sealed directly to the support web 2 as shown in Figure 1. The peelable film does not contact the carrier web 2 as its function is to provide a removable gas barrier allowing oxygen to penetrate through the remaining skin film 5 and create bloom on the beefsteak product 8 in the manner described in the above-mentioned US-A-3 574 642.

The barrier film or peelable film 4 is preferably a multilayered gas impermeable film comprising a plurality of layers including a barrier layer comprising a material selected from the group consisting of hydrolyzed ethylene/vinyl acetate copolymers (EVOH) and vinylidene chloride copolymers (PVDC). A specific forming web which has been found to be satisfactory and which is the best embodiment of a forming web structure at the time of the filing of this application is a forming web which is separable into the permeable skin layer 5 and the impermeable peelable layer 4 and which has the following detailed design features:

Skin or seal layer 5

Sealing layer/core layer/optical layer

0.20-0.60 1.75-2.50 0.10-0.20 mils thickness,

where:

Sealing material = VLDPE from Union Carbide or EVA copolymer with 4 to 12% VA from DuPont,

Core = VLDPE or EVA copolymer with 18 to 28 % VA content and

Optical = ULDPE from Dow, resins 4002A or 4002B is.

Peelable layer 4

EVOH/LDPE(link) + HDPE/EVOH/LDPE(link) + HDPE/EVA/HDPE(outer)

40% 60% 40% 60%

0.20 0.20 0.20 0.20 1.5 0.20 mils thickness,

where:

EVOH = Ethylene/Vinyl Alcohol from Evalca is,

LDPE(link) = adhesive, preferably Binell from DuPont,

EVA = EVA copolymer with 18 % VA and

HDPE = High Density Polyethylene from USI is.

In the preferred peelable film given above, it can be seen that in order to obtain very good barrier properties, two layers of EVOH are used. The first EVOH layer is the interface with the ULDPE layer in the sealing film 5. The interface layers EVOH and ULDPE are relatively incompatible polymers and when co-extruded together form a very weak interface and can be easily pulled apart.

To produce the composite film or sheet, a coextrusion process similar to that described in US-A-4 287 151 to Esakov et al. on September 1, 1981 may be used. Of course, suitable annular multilayer dies must be used used and these are known to those who are familiar with the technique of coextrusion of thermoplastic multilayer films.

The preferred film described above seals to a saran coated PVC carrier web with an adhesion strength greater than the strength required to delaminate the release film 4 from the skin film 5 as shown in Figure 2.

In Figure 3, on the right hand side, a vacuum skin packaging chamber 10 is shown, and on the left hand side of Figure 3, a separating or cutting station 11 is shown. Before entering the vacuum skin packaging station 10, the products 8 have been arranged on a carrier element 2 in rows and columns using a vacuum skin packaging process, preferably according to the process described in the above-referenced US-RE 30 009. Another patent publication which discloses that a product is arranged on a carrier element, vacuum skin packaged and then cut and separated from the carrier web is GB-A-2 130 166, issued on December 17, 1986.

In the present invention, once the product has been loaded onto the support member 2 in rows and columns as shown in Figure 3 and prior to entry into the vacuum skin packaging chamber 10, a tape strip 6 is applied across the support member 2 between each column of products 8. This film, which has an adhesive surface to adhere to the support sheet 2, has a non-adhesive upper surface 7 which may be a surface having a wax coating, Teflon or similar material to which the skin or sealing film 5 does not adhere during the vacuum skin packaging process. Thus, the packages 8, when they emerge from the vacuum skin packaging chamber 10, have a cross-section shown schematically by the enlargement in Figure 4, where it will be seen that the tape 6 is preferably arranged between the columns of packages 8 on the centre line of these columns. As an alternative to using a tape, a non-adhesive material may be coated onto the film in this position, such as with a roller similar to a printing roller, which produces such a coating across the carrier web 2.

The perforation step, described in more detail below, may be carried out before entering the cutting station 11 or in connection with the cutting process or a column of products 8 may be removed or severed from the continuous carrier web 2 as shown in Figure 7. The line of perforations 17 is preferably arranged in the manner shown in Figures 5 and 6.

In Figures 5 and 6 there are shown perforating blades 15 which are balanced by a rack 14 above the forming web 3 in the area immediately adjacent to the non-adhesive strip 6 so that when the perforating needles or blades 15 are driven downwards they penetrate as shown in Figure 6 with the result that the non-adhesive area 6 is not penetrated but the layers 4 and 5 are completely penetrated all the way into the carrier web 2. It has surprisingly been found that in order to produce an effective line of perforations as shown in Figures 7 and 8 the perforations must be spaced from the non-adhesive strip 6. Any suitable blade, needle or hole punch will serve this purpose, including the use of a serrated knife, as long as the small holes or perforations are cut into the package immediately adjacent to the header strip or non-adhesive strips 6. Because this film is not sealed over the non-adhesive strip 6, it provides a grip strip as illustrated in Figure 1.

In Figure 1, the manual gripping strip 18 formed as explained above is shown partially separated from the forehead or non-adhesive tape 6 and the perforation line left by the action of the needle or punch 15 is shown. When the strip 18 is pulled in the direction of the arrow in Figure 2, the sealable film 5 tears in the area adjacent to the forehead 6 where the perforation 9 has been made, leaving the sealed segment 5 sealed to the carrier web 2 and the torn segment 5" forming part of a pull tab which, when pulled further and rotated in the direction of the arrow, delaminates the barrier or peelable film 4 from the skin or permeable film 5. In this way, the product 8 remains completely covered by the permeable skin film 5.

The line of perforations magnifies the tearing action and provides a straight line along which the tearing occurs. The spacing and size of the holes is determined by the thickness of the film and the different film compositions and such determination can be made by one skilled in the art. For the thickness of the films of the preferred forming web as indicated above, a perforation distribution of 1 per 5 mm (5 per inch), each perforation being about 1.6 mm (1/16 inch) in width, has been found to be satisfactory. From testing, it has been shown that smaller holes spaced closer together work more satisfactorily. It is of course necessary that the breaking or tearing strength of the perforated barrier film 4 be greater than that of the perforated sealable film 5. The line of perforations appears to accentuate the difference in tearing strength and allows for easier tearing. In this way, a beefsteak which, for example, has been stored in a vacuum package for a period of 14 to 28 days and during which the beefsteak was purple in colour will now usually bloom in its bright red colour within 30 minutes to 1 hour after the peelable barrier layer has been removed and the surface of the meat is exposed to oxygen as it passes through the foil.

An alternative way of applying the perforations is to use a serrated wheel rolled across the columns of packages in suitable areas adjacent to the forehead.

The forehead may also have inclusions or other descriptive information on the non-adhesive surface 7, since the package 1 from which the peelable film 4 has been removed is the package present in the sales display case in the supermarket.

Upon reading and becoming familiar with the disclosure, equivalent film combinations and packaging configurations will become clear and apparent to those skilled in the art. The present invention is, however, limited only by the scope of the following claims.

Claims (17)

1. Packaging (1) with a removable film layer (4), which (a) a product (8), (b) a carrier web (2) on the upper surface of which the product (8) lies, the carrier web (2) having at least one edge, (c) a composite film (3) as a forming web enclosing the product (8), the composite film (3): (1) a skin layer (5) sealed around the periphery of the product (8) to the carrier web (2), and (2) a peelable layer (4) laminated or co-extruded onto the skin layer (5) on the outside of the package, the adhesive strength between the peelable layer (4) and the skin layer (5) being of such a strength that the two layers can be separated manually from each other, and the adhesive strength being less than the seal strength between the skin layer (5) and the carrier web (2), (d) non-adhesive means (6) arranged along an edge of the support element (2) to prevent sealing of the forming web (3) to the support web (2) in the area of the non-adhesive means (6), whereby the unbonded forming web (3) forms a strip for manual pulling (18), and (e) a line of perforations (9, 17) as means for initiating peeling, adjacent to and along the length of the non-adhesive means (6) on the side of the non-adhesive means opposite the edge means (6), the means for initiating the peeling (9, 17) initiating the tearing of the area of the skin layer (5'') lying over the non-adhesive means (6) from the rest of the skin layer (5'), whereby when the pull strip (18) is pulled away from the carrier web (2), the peeling of the peelable layer (4) from the skin layer (5) is initiated, (f) wherein the tear strength of the peelable layer (4) along the line of perforations (17) is greater than that of the skin layer (5), whereby when the manual pulling strip (18) is grasped and lifted, the peelable film (4) does not tear along the line, but the skin layer (5) tears as it remains sealed to the carrier web (2) while the peelable layer (4) is peeled off. 2. Packaging according to claim 1, wherein the means for initiating the peeling are a series of perforations (17) penetrating the forming web (3). 3. A package according to claim 2, wherein the series of perforations lie in a substantially straight line. 4. Packaging according to one of claims 1 to 3, in which the supporting web is gas-impermeable. 5. Packaging according to one of claims 1 to 4, in which the peelable layer is gas-impermeable. 6. A package according to claim 5, wherein the peelable layer comprises a plurality of layers of thermoplastic material, at least one of which is a gas barrier layer. 7. A package according to any one of claims 1 to 5, wherein the skin layer comprises a plurality of layers of thermoplastic film and the skin layer has a relatively high oxygen permeability. 8. A package according to claim 7 when appended to claim 6, wherein the interior of the package containing the product has been evacuated. 9. Packaging according to one of claims 1 to 3, in which the supporting web (2) is a semi-rigid web of thermoplastic material with a gas barrier coating or layer and the composite film (3) is a forming web which has been formed around the product by a vacuum skin packaging process and sealed to the supporting web around the periphery of the product, comprises as a skin layer a gas-permeable multilayer skin film forming the surface of the forming web (3) which has been sealed to the supporting web (2), and as a peelable layer (4) a peelable multilayer film with a gas barrier layer. 10. Packaging according to one of claims 1 to 9, in which the carrier web (2) comprises a thermoplastic base. 11. Packaging according to claim 10, wherein the forming web has been formed by a coextrusion process. 12. Packaging according to one of claims 1 to 11, in which the non-adhesive means (6) consist of a front strip with non-adhesive surface (7) which is opposite to the composite film (3), the composite film (3) lying over the front strip but not adhering to it, both the front strip and the composite film (3) end at the edge of the support element (2), whereby the composite film (3) can be easily separated from the front strip at the edge and thus forms the strip for manual pulling (18). 13. Packaging according to one of claims 7 to 12, in which the product is a fresh meat product. 14. Vacuum skin packaging process in which a product is packaged between a forming web (3) and a carrier web (2) and in which: (a) a non-adhesive surface (7) is formed adjacent to an edge of the carrier web (2), (b) a forming web (3) is formed with manually separable layers comprising a peelable barrier film (4) and a gas-permeable skin film (5), the tear strength of the skin film (5) being lower than that of the peelable film (4), (c) a vacuum skin package is formed, wherein the forming web (3) is sealed to the carrier web (2) around the periphery of the product (8), the product (8) is spaced from the non-adhesive surface (7) and the non-sealed region of the forming web (3) above the non-adhesive region (7), thereby forming a strip for manual pulling (18), and the sealing strength of the skin film (5) to the carrier web (2) is greater than the tear strength of the skin film (5), and (d) the forming web (3) is perforated with a plurality of perforations (17) in a line adjacent to the non-adhesive surface (7), whereby when the pull tab (18) is manually pulled away from the carrier element (2), the skin film (5) tears and releases the peelable film (4) to be peeled off the skin film (5). 15. A method according to claim 14, wherein the step of forming a non-adhesive surface (7) comprises adhering a strip of adhesive tape or other material having a non-adhesive surface (7) to the carrier web (2) adjacent an edge thereof. 16. A method according to claim 14 or 15, wherein the step of forming the vacuum skin package comprises forming a plurality of vacuum skin packages by arranging a plurality of products on a continuous support member in an arrangement of rows and columns, and thereafter vacuum skin packaging at least one column at a time as the support member is moved towards the rows. 17. A method according to claims 15 and 16 taken together, including the steps of applying a strip of adhesive tape or non-sealable material across the width of the carrier web between the columns prior to vacuum skin packaging the respective column and then cutting the carrier web and tape approximately at the center line of the tape and between the rows to form individual, easily peelable packages.